Field of the Invention
The present invention relates to a hybrid electric vehicle, and more particularly to a control method and apparatus of a hybrid electric vehicle.
Discussion of the Related Art
Hybrid electric vehicles (hereinafter, referred to as “hybrid vehicles”) may have various power transmission apparatuses using an engine and a motor as a power source. These power transmission apparatuses include a series type, a parallel type, a power split type, etc. The hybrid vehicle may be driven in an electric vehicle (EV) mode and a hybrid electric vehicle (HEV) mode. The EV mode is a mode in which the vehicle is driven through driving of the motor based on power of a battery.
In addition, when the battery or a power electric (PE) part (e.g., a motor or a generator) fails during operation, to protect the battery/PE part and to prevent a safety accident from occurring due to abnormal operation, an emergency mode (e g, limp-home mode), in which a relay for intermitting power connection of the battery is cut off and the vehicle is driven using power of the engine, is executed. Particularly, when freewheeling of the motor/generator is performed by power of the engine, counter electromotive force occurs. However, when such counter electromotive force is substantial, the battery which may absorb counter electromotive force, is isolated and, thus, for example, inner pressure of a switch (IGBT) of an inverter is increased and the inverter may be burn out.
For example, among parallel type systems, there is a type in which an engine clutch is disposed between an engine and a motor, and a drive shaft is driven by the motor when the engine clutch is open and driven by the engine and the motor when the engine clutch is locked up. In particular, when a driving apparatus of a hybrid vehicle fails, for example, when a battery or a motor is abnormally operated, to prevent damage to main PE parts (e.g., a motor, a low voltage DC-DC (LDC) converter, and a battery) of the hybrid vehicle and other vehicle parts and to prevent a traffic accident from occurring due to abnormal operation of the battery or the motor, the hybrid vehicle performs a driving process in which a main relay connected to the battery is turned off and the engine clutch is connected to use power of the engine.
By connecting the engine clutch, the motor shares one drive shaft connected to the engine with the engine and thus the motor is freewheeled. Particularly, counter electromotive force is generated from the motor by rotation of the drive shaft and the intensity of counter electromotive force may be increased by high-speed rotation of the drive shaft.
In an isolated situation of the battery for absorbing counter electromotive force generated by turning off the main relay, internal voltage of an insulated gate bipolar mode transistor (IGBT) performing a switching function and included in an inverter within the motor is increased by counter electromotive force and, when voltage exceeding an allowable voltage (e.g., internal voltage) is applied, burn-out of the inverter, such as degradation or dielectric breakdown of the inverter, may occur. Therefore, a cooperative control method, in which burn-out of an inverter of a motor (including a hybrid starter generator (HSG)) caused by high-speed rotation is prevented while maintaining the locked-up state between an engine and the motor by an engine clutch in a failure situation of a hybrid vehicle, is required.